Plasma transfer welded arc torch

Abstract

A plasma arc torch is disclosed having an upper body of a non-conductive material supporting an electrode and a lower body of a conductive material supporting a nozzle through which an arc is formed between the electrode and a work piece. Means is provided for blowing a mixture of inert gas and a fusible powder through a passageway formed in said lower body and through passages formed in said nozzle onto the work piece. A liquid coolant is circulated through a reservoir formed in the lower body, and an inert gas is discharged through an opening that circumvallates the nozzle. Both the nozzle and the torch as a whole are uniquely constructed to avoid many of the problems caused by the use of insulators and fluid seals. In addition, the novelty of construction enhances performance.

What is claimed is: 
     
       1. A plasma arc torch having upper and lower body members formed with coaxial passages, an electrode supported from said upper body member within said coaxial passages, and a nozzle having an axial arc port through which an arc is formed between the electrode and a work piece, said lower body member comprising an outer metallic shell and an inner metallic sleeve, said outer shell having a plurality of passageways formed therein including at least one passageway for connecting a coolant reservoir with an external source of coolant, a second passageway for connecting a pressurized mixture of powder and inert gas with said nozzle, and a third passageway for connecting a shield gas with an annular discharge that encircles the nozzle, the lower end of said inner metallic sleeve being internally threaded, said nozzle having a powder-gas discharge plate supported on a tubular stem threadably engaged with the lower end of said sleeve, said powder-gas discharge plate having a plurality of passages extending from an upper face to a lower face, said passages being angularly directed, convergent and circumferentially spaced around the axial arc port of said nozzle; and an annular plenum defined between the upper face of said powder-gas discharge plate and the lower end of said outer metallic shell, said annular plenum being in communication with the second passageway and the plurality of passages. 
     
     
       2. The plasma arc torch of claim 1, the upper face of said powder-gas discharge plate being formed with an annular groove, the ends of the plurality of passages formed in said plate terminating within said groove, said groove defining one portion of the plenum for a powder-gas mixture. 
     
     
       3. The plasma arc torch of claim 1 said outer metllic shell having an upper annular flange, said third passageway being formed through said flange interconnecting a radial inlet port with a discharge port formed in the underside of said flange. 
     
     
       4. The plasma arc torch of claim 1, said upper body member being formed of a machinable, electrical insulating material; and an electricaly conductive holder threadably mounted to said upper body member for supporting said electrode in spaced relation to said lower body member and nozzle. 
     
     
       5. The plasma arc torch of claim 4 and further comprising means supported upon said upper body for cooling said electrode. 
     
     
       6. The plasma arc torch of claim 1, the lower end of said lower body being dished to receive the powder-gas discharge plate. 
     
     
       7. The plasma arc torch of claim 4 and further comprising a spacer sleeve formed of insulating material received within the upper end of said shell and lodged between said electrically conductive holder and said nozzle. 
     
     
       8. A plasma arc torch having upper and lower body members formed with coaxial passages, an electrode supported from said upper body member and within said coaxial passages, and a nozzle supported from the lower end of said lower body member, said nozzle having an axial passage through which an arc is formed between the electrode and a workpiece, said lower body member and nozzle define an annular plenum, said lower body member being formed with a passageway for connecting a pressurized mixture of powder and inert gas with said annular plenum, said nozzle having a plurality of passages in open communication with said annular plenum, each passage being angularly directed and convergent with respect to the axial passage and circumferentially spaced around said axial passage, whereby a pressurized mixture of powder and inert gas is passed through said lower body member into the annular plenum and convergently directed through the plurality of passages formed in the nozzle, said lower body member being internally threaded, said nozzle having a powder-gas discharge plate supported on a tubular stem threadably engaged with the lower body member. 
     
     
       9. The plasma arc torch of claim 8, the upper face of said powder-gas discharge plate being formed with an annular groove, the ends of the pluraity of passages formed in said nozzle terminating wilhin said groove, said groove defining one portion of Lhe plenum for a powder-gas mixture. 
     
     
       10. The plasma arc torch of claim 8, the lower end of said lower body being dished to receivee the powder-gas discharge plate.